From f90615ada0b1e21a9d93ff89b04549fd7a92c92b Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Fri, 21 Apr 2023 01:55:53 +0300 Subject: net: vlan: don't adjust MAC header in __vlan_insert_inner_tag() unless set This is a preparatory change for the deletion of skb_reset_mac_header(skb) from __dev_queue_xmit(). After that deletion, skb_mac_header(skb) will no longer be set in TX paths, from which __vlan_insert_inner_tag() can still be called (perhaps indirectly). If we don't make this change, then an unset MAC header (equal to ~0U) will become set after the adjustment with VLAN_HLEN. Signed-off-by: Vladimir Oltean Reviewed-by: Eric Dumazet Reviewed-by: Simon Horman Reviewed-by: Florian Fainelli Signed-off-by: David S. Miller --- include/linux/if_vlan.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h index 6864b89ef868..90b76d63c11c 100644 --- a/include/linux/if_vlan.h +++ b/include/linux/if_vlan.h @@ -351,7 +351,8 @@ static inline int __vlan_insert_inner_tag(struct sk_buff *skb, /* Move the mac header sans proto to the beginning of the new header. */ if (likely(mac_len > ETH_TLEN)) memmove(skb->data, skb->data + VLAN_HLEN, mac_len - ETH_TLEN); - skb->mac_header -= VLAN_HLEN; + if (skb_mac_header_was_set(skb)) + skb->mac_header -= VLAN_HLEN; veth = (struct vlan_ethhdr *)(skb->data + mac_len - ETH_HLEN); -- cgit v1.2.3 From 1f5020acb33f926030f62563c86dffca35c7b701 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Fri, 21 Apr 2023 01:55:54 +0300 Subject: net: vlan: introduce skb_vlan_eth_hdr() Similar to skb_eth_hdr() introduced in commit 96cc4b69581d ("macvlan: do not assume mac_header is set in macvlan_broadcast()"), let's introduce a skb_vlan_eth_hdr() helper which can be used in TX-only code paths to get to the VLAN header based on skb->data rather than based on the skb_mac_header(skb). We also consolidate the drivers that dereference skb->data to go through this helper. Signed-off-by: Vladimir Oltean Reviewed-by: Eric Dumazet Reviewed-by: Simon Horman Reviewed-by: Florian Fainelli Signed-off-by: David S. Miller --- include/linux/if_vlan.h | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h index 90b76d63c11c..3698f2b391cd 100644 --- a/include/linux/if_vlan.h +++ b/include/linux/if_vlan.h @@ -62,6 +62,14 @@ static inline struct vlan_ethhdr *vlan_eth_hdr(const struct sk_buff *skb) return (struct vlan_ethhdr *)skb_mac_header(skb); } +/* Prefer this version in TX path, instead of + * skb_reset_mac_header() + vlan_eth_hdr() + */ +static inline struct vlan_ethhdr *skb_vlan_eth_hdr(const struct sk_buff *skb) +{ + return (struct vlan_ethhdr *)skb->data; +} + #define VLAN_PRIO_MASK 0xe000 /* Priority Code Point */ #define VLAN_PRIO_SHIFT 13 #define VLAN_CFI_MASK 0x1000 /* Canonical Format Indicator / Drop Eligible Indicator */ @@ -529,7 +537,7 @@ static inline void __vlan_hwaccel_put_tag(struct sk_buff *skb, */ static inline int __vlan_get_tag(const struct sk_buff *skb, u16 *vlan_tci) { - struct vlan_ethhdr *veth = (struct vlan_ethhdr *)skb->data; + struct vlan_ethhdr *veth = skb_vlan_eth_hdr(skb); if (!eth_type_vlan(veth->h_vlan_proto)) return -EINVAL; @@ -713,7 +721,7 @@ static inline bool skb_vlan_tagged_multi(struct sk_buff *skb) if (unlikely(!pskb_may_pull(skb, VLAN_ETH_HLEN))) return false; - veh = (struct vlan_ethhdr *)skb->data; + veh = skb_vlan_eth_hdr(skb); protocol = veh->h_vlan_encapsulated_proto; } -- cgit v1.2.3 From 0bcf2e4aca6c29a07555b713f2fb461dc38d5977 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Fri, 21 Apr 2023 01:56:01 +0300 Subject: net: dsa: tag_ocelot: call only the relevant portion of __skb_vlan_pop() on TX ocelot_xmit_get_vlan_info() calls __skb_vlan_pop() as the most appropriate helper I could find which strips away a VLAN header. That's all I need it to do, but __skb_vlan_pop() has more logic, which will become incompatible with the future revert of commit 6d1ccff62780 ("net: reset mac header in dev_start_xmit()"). Namely, it performs a sanity check on skb_mac_header(), which will stop being set after the above revert, so it will return an error instead of removing the VLAN tag. ocelot_xmit_get_vlan_info() gets called in 2 circumstances: (1) the port is under a VLAN-aware bridge and the bridge sends VLAN-tagged packets (2) the port is under a VLAN-aware bridge and somebody else (an 8021q upper) sends VLAN-tagged packets (using a VID that isn't in the bridge vlan tables) In case (1), there is actually no bug to defend against, because br_dev_xmit() calls skb_reset_mac_header() and things continue to work. However, in case (2), illustrated using the commands below, it can be seen that our intervention is needed, since __skb_vlan_pop() complains: $ ip link add br0 type bridge vlan_filtering 1 && ip link set br0 up $ ip link set $eth master br0 && ip link set $eth up $ ip link add link $eth name $eth.100 type vlan id 100 && ip link set $eth.100 up $ ip addr add 192.168.100.1/24 dev $eth.100 I could fend off the checks in __skb_vlan_pop() with some skb_mac_header_was_set() calls, but seeing how few callers of __skb_vlan_pop() there are from TX paths, that seems rather unproductive. As an alternative solution, extract the bare minimum logic to strip a VLAN header, and move it to a new helper named vlan_remove_tag(), close to the definition of vlan_insert_tag(). Document it appropriately and make ocelot_xmit_get_vlan_info() call this smaller helper instead. Seeing that it doesn't appear illegal to test skb->protocol in the TX path, I guess it would be a good for vlan_remove_tag() to also absorb the vlan_set_encap_proto() function call. Signed-off-by: Vladimir Oltean Reviewed-by: Simon Horman Reviewed-by: Florian Fainelli Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/if_vlan.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'include') diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h index 3698f2b391cd..0f40f379d75c 100644 --- a/include/linux/if_vlan.h +++ b/include/linux/if_vlan.h @@ -685,6 +685,27 @@ static inline void vlan_set_encap_proto(struct sk_buff *skb, skb->protocol = htons(ETH_P_802_2); } +/** + * vlan_remove_tag - remove outer VLAN tag from payload + * @skb: skbuff to remove tag from + * @vlan_tci: buffer to store value + * + * Expects the skb to contain a VLAN tag in the payload, and to have skb->data + * pointing at the MAC header. + * + * Returns a new pointer to skb->data, or NULL on failure to pull. + */ +static inline void *vlan_remove_tag(struct sk_buff *skb, u16 *vlan_tci) +{ + struct vlan_hdr *vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN); + + *vlan_tci = ntohs(vhdr->h_vlan_TCI); + + memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN); + vlan_set_encap_proto(skb, vhdr); + return __skb_pull(skb, VLAN_HLEN); +} + /** * skb_vlan_tagged - check if skb is vlan tagged. * @skb: skbuff to query -- cgit v1.2.3